This invention relates generally to permanent magnet synchronous motors constructed from rotor/stator component sets, or direct drive torque motors. These motors have been used for many years to optimize the space and performance of machines. The performance advantages are well known and include zero maintenance, clean mechanical assembly, reduced number of parts, better servo performance, better accuracy, and quiet operation.
Their use, however, has been limited to very special applications, which absolutely require their performance benefits. This is due to the very difficult integration and design time created by the use of frameless parts sets (rotor/stator) in an application. Quite often long periods of engineering consultation and design are required (along with Non-Recurring Engineering funds) to realize an implementation.
This difficulty results because these sets do not necessarily have housings or bearings which maintain a mechanical air gap between the rotor and stator components. The large magnetic forces between the rotor and stator, therefore, make assembly into a machine difficult, the difficulty increasing with the size of the motor. Considerable work, tooling and care must be taken to allow safe (to both people and the mechanism) and smooth insertion of the rotor component into the stator.
It is known in the art to solve some of the problems listed above using a rotor/stator combination where the rotor is aligned and locked to a housing holding the stator. In these prior art systems this locking is accomplished by bolting the rotor flush to the housing. Such a system, however, requires significant axial movement of the rotor during installation thereby creating difficulties during installation. Further difficulty is experienced because a feedback device must be mounted and angularly aligned at the time of installation, a delicate process requiring specialized equipment.
The safety, ease of assembly, and cost of integration problems described above are addressed by this invention.
The above identified problems are solved and a technical advance is achieved in the art by providing a frameless cartridge motor in accordance with the present invention.
The idea behind the cartridge motor of the present invention is to lessen the integration and application time for the motor and thereby make it easier to use for more applications. In the ultimate implementation of the idea, a motor (stator and rotor), housing, and feedback device are supplied as a single unit that can simply be mounted without the need to adjust the motor or mount or adjust the feedback device.
A cartridge motor is presented with an integral feedback device, so the motor can be mounted quickly and easily. To accomplish this the present invention provides a flexible mount for the feedback device that allows the installation of the feedback device at the factory where the motor is produced. In this arrangement the feedback device is already xe2x80x9czeroedxe2x80x9d to the motor electromagnetics so that the electronic commutation is correct. Without the use of the present invention mounting the feedback device is cumbersome. It is also inaccurate since special equipment is needed to align or xe2x80x9czeroxe2x80x9d the device with the motor. So, the process becomes longer, more expensive, and tends to eliminate the advantages of the cartridge motor. The ideas in this disclosure allow the customer to mount an entire motor assembly in minutes, plug a cable in and run.
In an alternate embodiment a cartridge motor is presented with fasteners that do not require significant axial movement at the time of installation. This arrangement similarly reduces installation complexity.
Accordingly, it is an object of the present invention to provide a direct drive cartridge motor comprising a housing, a stator, a rotor and a fastener. Where the fastener is used to lock the rotor to the housing in an aligned and calibrated configuration for shipping, without requiring extensive axial movement at the time of installation.
It is a further object of the invention to provide a direct drive cartridge motor with an integrated feedback device comprising a housing, a rotor, a stator, a fastener and a feedback device mounted to the motor via a flexible member. Where the fastener is used to lock the rotor, stator and housing in an aligned and calibrated configuration for shipping. And, the flexible member keeps the feedback device angularly aligned with the motor, while allowing some degree of movement in other directions.
It is a further object of the present invention to provide a method for assembling a direct drive cartridge motor comprising, aligning a rotor and a stator, mounting a feedback device on to the motor with a flexible member, aligning the feedback device and fixing the rotor in its aligned configuration for shipment.
Other and further aspects of the invention will become apparent during the course of the following description and by reference to the attached drawings.